Recently, there has been a spread of contents distribution which distributes contents including moving pictures and audios via a network. Under such circumstances, as a method of efficiently transmitting moving picture data, there is often used a method of transmitting data that is encoded by high-efficient compression based on inter-frame prediction, for example. In these methods, data of prediction parameter obtained by predicting encoded picture from the preceding and following frames in terms of time and the prediction residual picture data are encoded so as to reduce the information amount of the moving picture data which have high correlation in the time direction. Furthermore, the prediction residual picture data is compression-encoded highly efficiently through conversion-encoding and quantization, thereby enabling transmission of contents data with less transmission band.
Typical examples thereof are methods which use compression encoding systems such as MPEG (Moving Picture Experts Group)-1, MPEG-2, and MPEG-4. In these compression encoding systems, inter-frame prediction by motion compensation is performed on the input picture frames by a rectangular area unit of a constant size called a macro block. The obtained motion vector data and signal data that is obtained by compressing the prediction residual picture data through application of two-dimensional discrete cosine conversion and quantization are variable-encoded.
Moreover, for audios, there is also an audio compression method directed to the data encoded by high-efficient compression based on inter-frame prediction such as AAC (Advanced Audio Codec). By employing this method, it becomes possible to distribute the contents data by efficiently utilizing the transmission band of the network.
There are a great number of methods for distributing such contents compression-encoded information to IP (Internet Protocol) network that utilizes a packet switching system. Further, it is expected in the future that such methods be developed into distribution of contents in a mobile communication system. The mobile communication system is a system where mobile stations constituted with PHS (Personal Handyphone Systems), portable telephones, and portable terminals utilizing those as a means for communication are connected through radio stations and radio channels.
There is also known scalable encoding which is capable of varying resolution and picture quality multi-hierarchically (for example, Patent Literature 1)
Patent Literature 1: Japanese Unexamined Patent Publication 9-98434